An important technical problem exists in that rare gas having high polarization rate is achieved by a conventional NMR device.
Herein, the polarization means that the distribution of the number of spins occupying an energy level of a nuclear spin of the atomic nucleus corresponding to the state for the distribution to a main static magnetic field is extremely biased in comparison with the distribution at the thermal equilibrium.
Due to irradiation by circularly polarized excitation light to a mixed with gases, wherein rare gas of the spin quantum number 1/2 of xenon-129(129Xe), helium-3(3He) or the like containing a monatomic molecule having the nucleus spin is mixed with alkali metal steam such as rubidium (Rb) and cesium (Cs), an electron of the ground state level according to rubidium and the like is excited by photoabsorption, followed by being excited to the excitation state level and returning to the ground state level, at one time, the electron likely transits to one level of the electron levels in the ground state level in which the degeneracy is magnetically released by the magnetic field impressed from the outside; thereby the state having the high electron spin polarized degree of the rubidium molecule or the like is produced. The rubidium or the like having the high polarized state is collided with the rare gas xenon or the like, and the high polarized state of the rubidium or the like is moved to the nucleus spin system of the rare gas of the xenon or the like in the process. Thereby, the rare gas having the polarized state is obtained. [W. Happer, E. Miron, S. Schaefer, D. Schreiber, W. A. van Wijngaarden, and X. Zeng, Phys. Rev. A29, 3092 (1984).]. In general, the process is called an optical pumping.
The following device is known as a conventional device for producing the polarized gas. The mixture gas of a rare gas and alkali metal steam is enclosed in an optical reactive container, and the mixture gas is irradiated with the excitation light and the magnetic field is impressed to the mixture gas. For example, for the sake of using the polarized helium-3 having the high density as a neutron polarizer, the mixture gas of helium-3 gas and nitrogen, and an alkali metal are enclosed in a cylindrical glass ampoule, and thereby the polarized gas is produced. [M. E. Wagshul and T. E. Chupp, Phy. Rev. A40, 4447 (1989).].
The following method is known as a device in which the polarized rare gas of xenon-129 is applied to the nuclear magnetic resonance measurement (NMR) and the magnetic resonance imaging measurement (MRI). The method wherein NMR signal of the polarized xenon-129 is measured by using xenon-129 and rubidium introduced to the cylindrical glass container, and also the method of measuring the NMR signal of the proton-1 is measured whereby spin polarization is forwarded by applying nucleus Overhauser effect to the proton-1 nucleus from the polarized xenon-129 nucleus [D. Raftery, H. Tong, T. Meersmann, P. J. Grandinetti, L. Reven, and A. Pines, Phy. Rev. Lett. 66, 584 (1991) and G. Navon, Y.-Q. Song, T. Room, S. Appelt, R. E. Taylor, and A. Pines, Science 271, 1848 (1996)], is known. It is also known the polarized xenon-129 is introduced to an animal to measure the image of a cave such as a lung [M. S. Albert, G. D. Cates, B. Driehuys, W. Happer, B. Saam, C. S. Springer Jr., and A. Wishnia, Nature 370, 199 (1994) and U.S. Patent (U.S. Pat. No. 5,545,396 (1996)].
In any case, the operation for improving the polarization rate is performed by entering the excitation beam from one direction in the state where the rare gas or the like is stayed in a light response container. When the polarization rate rises, the rare gas or the like is cooled off, and is used as the neutron polarizer. The polarized rare gas is transported from the glass vessel to another container, and is used for NMR measurement or the like.
On the other hand, the following device and method are known as a device and a method for producing the polarized rare gas while making the gas flow. For example, xenon-129 of 1% is mixed with a buffer-gas of helium-4 gas of about 10 atmospheres, and the mixture is introduced to a cylindrical glass container. The mixture is irradiated with the excitation beam in parallel to the flow of the gas. That is, such an irradiation is carried out from the gas exit side of the container of the column bottom direction of the cylindrical glass container to the introduction side. From the gas exit of the container, the polarized mixed gas is induced in a dewar cooled off by a liquid nitrogen, and following separating the polarized xenon-129 as a solid, and being exhausted from a bentline. [B. Driehuys, G. D. Cates, E. Miron, K. Sauer, D. K. Walter and W. Happer, Appl. Phys Lett 69,1668 (1996).].
In addition, in the polarized rare gas production device that the inventors of the application have proposed, the polarized rare gas is produced while making the gas flow safely near the normal pressure by using the flow cell, and a nuclear magnetic resonance device is arranged backward thereof; thereby, NMR measurement can be performed in a short time without decreasing the polarization rate after polarized rare gas is continuously generated [Hattori, Hiraga, Nakai, Moriya, John M. Tracy, Japanese Unexamined Patent Application Publication No. 11-309126].
However, in a device wherein the gas or the like is stayed in a conventional cylindrical glass and the gas is excited and polarized, the strength of the excitation light, depending on the distance from the plane of incidence in the direction of the incidence, is exponentially decreased. The density of rubidium or the like in the cylindrical glass container is optimized and determined to the part where excitation light is strong; thereby, in a part which is away from the plane of incidence and in which the excitation light is weak and occupies a considerable volume.
Molecules such as xenon are moved to the part having high efficiency by diffusion and convection, and thereby the decrease in the polarization rate in the part having low excitation efficiency is dissolved. But, the decrease in the polarization rate causes the decrease in the entire excitation efficiency.
A problem exists in that in a conventional device which stays gas or the like, and in which the gas is polarized, the polarized rare gas can not be continuously generated, and time is required for taking out the polarized gas to another container separately and carrying to the NMR device or the like, and the polarization rate is decreased in the mean time.
On the other hand, in a device which produces the polarized rare gas while making the gas flow, the following problems exists. Since the buffer gas of the high pressure is introduced so as to reduce the los of the polarization rate due to the intermolecular collision of the polarized xenon-129, there is a danger of handling a gas. In addition, the polarized xenon-129 solidified is heated again and must be taken out to a cool dewar, and the time is required for NMR measurement. In addition, the amount of xenon-129 polarized actually by the device is about 5%.
Further, the excitation light is incidence only from one direction in the device which the polarized rare gas is produced while the gas is made to flow near the normal pressure by using the flow cell that inventors of the application, have already proposed. Thereby a problem exists in that the polarization rate is decreased in a part away from the light source.
Therefore, the invention of this application dissolves the conventional problem described above. It is a subject of the invention of this application that a polarized rare gas production device in which the polarization rate is improved while the gas is safely made to flow, and a polarized rare gas production using the device are proposed by making the best use of the features of a device and a method that inventors of the application have proposed and improving the cellular shape and the excitation light source. The subject of the invention of the application is to provide a nuclear magnetic resonance detection device which NMR and MRI measurement can be performed in a short time and without decreasing the polarization rate after the polarized rare gas is continuously generated by such an improved device and a method, and NMR and MRI measuring method using the inventive device and enabling a detection in a ultra small area with the high sensitivity and shortened measurement time.